In an earlier contribution to this discussion,
Tom wrote:

Most manufacturers seem to recommend setting flow rates in CH systems
to achieve a rise of 11deg across boiler, why is this? is it the most
efficient setting for heat transfer?
Tom

As others have stated, many systems are designed to run with a flow
temperature of 82 degC and a return temperature of 71 degC.

But why these particular values, I hear you cry? Well, it just so happens
that these correspond to 180 and 160 degF - with a 20 degree drop - all nice
round numbers!

So the whole thing dates from the time when temperatures were measured in
Fahrenheit, and energy in good old Britsh Thermal Units. [Wait for the
reaction to that one!] The values have simply been converted to Celsius.
--
Cheers,
Set Square
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